1. Field of the Invention
This invention relates to electronic musical instruments, and particularly to electronic organs of the type that feature automatic playing aids for the non-expert musician, such as automatic rhythm accompaniment.
2. The Prior Art
Electronic organs are now on the market with various automatic features which permit a player of less than expert skill to accomplish certain musical effects which would otherwise require years of training and practice. An example is automatic rhythm accompaniment. With this feature, the inexpert player can concentrate on producing the melody, while the instrument itself will automatically provide a rhythm accompaniment. Some of the instruments that are on the market employ digital techniques for generating and/or selecting musical notes, including the notes for the automatic rhythm accompaniment feature. In particular, these instruments employ read-only memories with various rhythm patterns stored therein to generate a repetitive accompaniment. These repetitive patterns, however, can easily seem artificial or "machine-made" after just a few repetitions, because they are lacking in richness and variety of pitch.
Often the particular digital technique used for pitch selection is pulse position modulation. In this method of pitch selection, the various keyboards and manuals, both upper and lower, are repeatedly scanned electronically from the higher to the lower pitches. For each key which is found to be depressed during a scan cycle, a pulse is generated at the appropriate time position in the scan. Thus, the occurrence of a pulse early in the scan cycle represents a relatively high pitch selection instruction, whereas the occurrence of such a pulse later on in the scan cycle represents a lower pitch instruction.
So far as is known, prior art musical instruments have neither recognized the desirability of, nor developed appropriate techniques for, the introduction of pitch multiplicity into the production of automatic accompaniment rhythm patterns. Prior art electronic musical instruments with automatic accompaniment generation capability have always produced a constant pitch register accompaniment. The resulting bass accompaniments have been characterized by a low order of musical interest, and they tend to sound somewhat artificial.